/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.hbase.client;

import java.io.IOException;
import java.net.UnknownHostException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.DoNotRetryIOException;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.HRegionLocation;
import org.apache.hadoop.hbase.NotServingRegionException;
import org.apache.hadoop.hbase.RemoteExceptionHandler;
import org.apache.hadoop.hbase.UnknownScannerException;
import org.apache.hadoop.hbase.client.metrics.ScanMetrics;
import org.apache.hadoop.hbase.conf.Configuration;
import org.apache.hadoop.hbase.ipc.RemoteException;
import org.apache.hadoop.hbase.net.DNS;
import org.apache.hadoop.hbase.regionserver.RegionServerStoppedException;

/**
 * Retries scanner operations such as create, next, etc.
 * Used by {@link ResultScanner}s made by {@link HTable}.
 */
public class ScannerCallable extends ServerCallable<Result[]> {
	public static final String LOG_SCANNER_LATENCY_CUTOFF = "hbase.client.log.scanner.latency.cutoff";
	public static final String LOG_SCANNER_ACTIVITY = "hbase.client.log.scanner.activity";
	private static final Log LOG = LogFactory.getLog(ScannerCallable.class);
	private long scannerId = -1L;
	private boolean instantiated = false;
	private boolean closed = false;
	private Scan scan;
	private int caching = 1;
	private ScanMetrics scanMetrics;
	private boolean logScannerActivity = false;
	private int logCutOffLatency = 1000;

	// indicate if it is a remote server call
	private boolean isRegionServerRemote = true;

	/**
	 * @param connection which connection
	 * @param tableName table callable is on
	 * @param scan the scan to execute
	 * @param scanMetrics the ScanMetrics to used, if it is null, ScannerCallable
	 * won't collect metrics
	 */
	public ScannerCallable(HConnection connection, byte[] tableName, Scan scan, ScanMetrics scanMetrics) {
		super(connection, tableName, scan.getStartRow());
		this.scan = scan;
		this.scanMetrics = scanMetrics;
		Configuration conf = connection.getConfiguration();
		logScannerActivity = conf.getBoolean(LOG_SCANNER_ACTIVITY, false);
		logCutOffLatency = conf.getInt(LOG_SCANNER_LATENCY_CUTOFF, 1000);
	}

	/**
	 * @param reload force reload of server location
	 * @throws IOException
	 */
	@Override
	public void connect(boolean reload) throws IOException {
		if (!instantiated || reload) {
			super.connect(reload);
			checkIfRegionServerIsRemote();
			instantiated = true;
		}

		// check how often we retry.
		// HConnectionManager will call instantiateServer with reload==true
		// if and only if for retries.
		if (reload && this.scanMetrics != null) {
			this.scanMetrics.countOfRPCRetries.inc();
			if (isRegionServerRemote) {
				this.scanMetrics.countOfRemoteRPCRetries.inc();
			}
		}
	}

	/**
	 * compare the local machine hostname with region server's hostname
	 * to decide if hbase client connects to a remote region server
	 * @throws UnknownHostException.
	 */
	private void checkIfRegionServerIsRemote() throws UnknownHostException {
		String myAddress = DNS.getDefaultHost("default", "default");
		if (this.location.getHostname().equalsIgnoreCase(myAddress)) {
			isRegionServerRemote = false;
		} else {
			isRegionServerRemote = true;
		}
	}

	public static int count = 0;

	public static boolean flag = false;

	/**
	 * @see java.util.concurrent.Callable#call()
	 */
	@SuppressWarnings("deprecation")
	public Result[] call() throws IOException {
		if (scannerId != -1L && closed) {
			close();
		} else if (scannerId == -1L && !closed) {
			this.scannerId = openScanner();
		} else {
			Result[] rrs = null;
			try {
				incRPCcallsMetrics();
				long timestamp = System.currentTimeMillis();
				rrs = server.next(scannerId, caching);

				if (logScannerActivity) {
					long now = System.currentTimeMillis();
					if (now - timestamp > logCutOffLatency) {
						int rows = rrs == null ? 0 : rrs.length;
						LOG.info("Took " + (now - timestamp) + "ms to fetch " + rows + " rows from scanner=" + scannerId);
					}
				}
				updateResultsMetrics(rrs);
			} catch (IOException e) {
				if (logScannerActivity) {
					LOG.info("Got exception in fetching from scanner=" + scannerId, e);
				}
				IOException ioe = null;
				if (e instanceof RemoteException) {
					ioe = RemoteExceptionHandler.decodeRemoteException((RemoteException) e);
				}
				if (ioe == null)
					throw new IOException(e);
				if (logScannerActivity && (ioe instanceof UnknownScannerException)) {
					try {
						HRegionLocation location = connection.relocateRegion(tableName, scan.getStartRow());
						LOG.info("Scanner=" + scannerId + " expired, current region location is " + location.toString() + " ip:"
								+ location.getServerAddress().getBindAddress());
					} catch (Throwable t) {
						LOG.info("Failed to relocate region", t);
					}
				}
				if (ioe instanceof NotServingRegionException) {
					// Throw a DNRE so that we break out of cycle of calling NSRE
					// when what we need is to open scanner against new location.
					// Attach NSRE to signal client that it needs to resetup scanner.
					if (this.scanMetrics != null) {
						this.scanMetrics.countOfNSRE.inc();
					}
					throw new DoNotRetryIOException("Reset scanner", ioe);
				} else if (ioe instanceof RegionServerStoppedException) {
					// Throw a DNRE so that we break out of cycle of calling RSSE
					// when what we need is to open scanner against new location.
					// Attach RSSE to signal client that it needs to resetup scanner.
					throw new DoNotRetryIOException("Reset scanner", ioe);
				} else {
					// The outer layers will retry
					throw ioe;
				}
			}
			return rrs;
		}
		return null;
	}

	private void incRPCcallsMetrics() {
		if (this.scanMetrics == null) {
			return;
		}
		this.scanMetrics.countOfRPCcalls.inc();
		if (isRegionServerRemote) {
			this.scanMetrics.countOfRemoteRPCcalls.inc();
		}
	}

	private void updateResultsMetrics(Result[] rrs) {
		if (this.scanMetrics == null || rrs == null) {
			return;
		}
		for (Result rr : rrs) {
			this.scanMetrics.countOfBytesInResults.inc(rr.getBytes().getLength());
			if (isRegionServerRemote) {
				this.scanMetrics.countOfBytesInRemoteResults.inc(rr.getBytes().getLength());
			}
		}
	}

	private void close() {
		if (this.scannerId == -1L) {
			return;
		}
		try {
			incRPCcallsMetrics();
			this.server.close(this.scannerId);
		} catch (IOException e) {
			LOG.warn("Ignore, probably already closed", e);
		}
		this.scannerId = -1L;
	}

	@SuppressWarnings("deprecation")
	protected long openScanner() throws IOException {
		incRPCcallsMetrics();
		long id = this.server.openScanner(this.location.getRegionInfo().getRegionName(), this.scan);
		if (logScannerActivity) {
			LOG.info("Open scanner=" + id + " for scan=" + scan.toString() + " on region " + this.location.toString() + " ip:"
					+ this.location.getServerAddress().getBindAddress());
		}
		return id;
	}

	protected Scan getScan() {
		return scan;
	}

	/**
	 * Call this when the next invocation of call should close the scanner
	 */
	public void setClose() {
		this.closed = true;
	}

	/**
	 * @return the HRegionInfo for the current region
	 */
	public HRegionInfo getHRegionInfo() {
		if (!instantiated) {
			return null;
		}
		return location.getRegionInfo();
	}

	/**
	 * Get the number of rows that will be fetched on next
	 * @return the number of rows for caching
	 */
	public int getCaching() {
		return caching;
	}

	/**
	 * Set the number of rows that will be fetched on next
	 * @param caching the number of rows for caching
	 */
	public void setCaching(int caching) {
		this.caching = caching;
	}
}
